The invention relates to the art of diagnosing engines and, more particularly, to diagnosing internal combustion engines while the crankshaft is rotating.
Whereas the invention is described herein in conjunction with compression ignition engines, the invention is not limited thereto as it may be used for testing other types of engines, such as spark ignition engines.
Engine analyzers are known in the prior art. Examples of prior art patents on this subject include the United States patents to Hanson U.S. Pat. No. 3,994,160, Hanson et al. No. 3,942,365, Hanson et al. No. 3,972,230, and Emerson No. 3,815,411. In general, each of these patents is directed toward a system for analyzing an engine operating with fuel being supplied so as to obtain an indication of power performance. In addition, these patents generally teach systems wherein an indication of engine speed and the contribution made by each cylinder is determined by examining the value of the time interval of each power period. The reciprocal of this value provides an indication of the average speed during the power period. By noting the various different levels of average speeds for various power periods, an indication of a low power performance is obtained.
The present invention is directed to improvements over that suggested by such prior art. In accordance with the present invention, the values of the time intervals between successive crankshaft positions are measured so as to obtain a plurality of time interval samples for each power period so as to obtain an accurate indication of the variations of engine speed throughout each power period. Also, in accordance with the present invention, at least two of these interval samples from each power period are employed for determining engine performance, such as compression and power performance levels.